Adorkable: Guren is adorable, often due to his earnest desire to help others and his occasional clumsiness.
Angst? What Angst?: Guren and Ceylan managed to avoid this for the most part in the first episode. Later all the boys are shown getting comfortable with their situation surprisingly quickly.
Arc Fatigue: The series was usually pretty good at avoiding this, but then came the Beast King Saga. For starters, it lasts several episodes, and seemingly has NO impact on the rest of the story, other than seeing Beag's Earth form. It also artificially increases its length by having Scorpidon keep changing the rules so he can force everyone to start over. By the 3rd episode even the knights are begging for this to end already. It gets to the point where the Knights and Villius get fed up with them and decide to just beat the stuffing out of them, which ends with Scorpidon finally letting them go.
Can't Un-Hear It: Many of the characters are voiced by famous anime voice actors, particularly the main four protagonists, so it's hard to listen to them and not think of other characters they did. (Example: Toxsa sounds exactly like Numbuh 2.)
Narm: "BEST" is abused and overused by Villius in Tenkai Knights Origins, at least on episode 3.
The Scrappy: Orangor and the Beast King, Scorpidon, for basically being one of the main reasons for causing a Hostile Show Take OverFiller Arc lasting 5 episodes (about 1/5th of season 2) that is seemingly completely irrelevant to the show's Myth Arc. Orangor has a shrill high-pitched voice and a Reality Warper that comes off as more annoying than funny. He usually ends up having the Knights and Beag chase him around and doing pointless contests, which leads to them and Vilius's troops trying to entertain the Scorpidon. Scorpidon is disliked for dragging out the arc by finding a way to keep changing the rules, thus causing them to start over.
Take That, Scrappy!: In the Arc's Final episode the Knights and Villius get fed up with it and decide to just beat them up.
They Wasted a Perfectly Good Character: The Tenkai Dragon, in the second season the dragon is reduced to what amounts to a few glorified cameos. Then an entirely new character, The Tenkai Wolf, (more a Deus ex Machina than a character, and was a product of the hated "Beast King Saga" referenced above) comes out of nowhere and helps save the heroes instead of the dragon.
They Wasted a Perfectly Good Plot: Wakamei learning about Quarton and the Tenkai Knights hasn't been brought up since the episode it happened. One could see her acting like Jazz from Danny Phantom, covering for him until he finds out she knows. Instead, the show goes on as if she never found out in the first place, thus depriving any development between Toxsa and his relationship with his sister.
Unintentionally Unsympathetic: While Gen's tragic past is supposed to inspire sympathy, he fails to illicit much pity when one realizes he's planning to wipe out life on two worlds in basically what amounts to a childish temper tantrum.
